1. Field of the Invention
The present invention relates to a flat display panel, and more particularly, to a liquid crystal display (LCD) panel having improved alignment stability and uniformity.
2. Description of the Related Art
Liquid crystal has both liquidity and orderly molecular arrangement, such as crystal of a solid state. In addition, the liquid crystal has optical anisotropy and has a characteristic in which, when a voltage is applied to a layer of the liquid crystal, the molecular arrangement of the liquid crystal is converted along a direction of an electric field. A device that displays graphics, characters, or figures using the property of the liquid crystal, is referred to as a liquid crystal display (LCD). The arrangement of the liquid crystal is converted depending on whether a voltage is applied to a layer of the liquid crystal. Thus, a voltage is selectively applied to the layer of the liquid crystal so that desired graphics or characters are displayed.
Typically, an LCD module, for example, a projection LCD module, includes an LCD panel comprising a liquid crystal panel, a driving circuit connected to the liquid crystal panel, and a backlight, which radiates light on one side of the liquid crystal panel. The liquid crystal panel includes liquid crystal, a color filter, an alignment film, and a polarization plate placed at both sides of the liquid crystal.
As shown in FIG. 1, a conventional LCD panel 10 includes a liquid crystal panel 12 and a driving circuit 14 placed around the liquid crystal panel 12. The liquid crystal panel 12 includes front glass plate FP and rear glass plate BP, which face each other, a common electrode (not shown) placed at a rear side of the front glass plate FP, and a display electrode layer (not shown) placed to face the common electrode. Liquid crystal is filled between the front glass plate FP and the rear glass plate BP and is in communication with the display electrode layer and the common electrode. The liquid crystal panel 12 further includes a polarization plate or a color filter. However, detailed descriptions thereof are common and thus will be omitted.
Referring to a circle showing an enlarged part of the liquid crystal panel 12 in FIG. 1, the liquid crystal panel 12 includes a thin film transistor (TFT) 12a which is a pixel driving device, and a display electrode 12b connected to a drain of the TFT 12a. A plurality of pixels are arranged in a matrix shape on the display electrode layer. The pixels consist of one TFT 12a and one display electrode 12b. Thus, a plurality of TFTs 12a and display electrodes 12b are arranged in a matrix shape on the display electrode layer. A source of each TFT 12a, corresponding to columns of the matrix shape, is connected in parallel to a data line DL, which is connected to a first driving circuit 14a of the driving circuit 14. A gate of each TFT 12a, corresponding to rows of the matrix shape, is connected in parallel to a gate line GL, which is connected to a second driving circuit 14b of the driving circuit 14. As such, a data line DL which corresponds to the number of columns of the matrix, is formed between the first driving circuit 14a and the liquid crystal panel 12, and a gate line GL which corresponds to the number of rows of the matrix, is formed between the second driving circuit 14b and the liquid crystal panel 12. The first driving circuit 14a applies a video signal to the liquid crystal panel 12 via the data line DL, and the second driving circuit 14b sequentially applies a scan signal to the liquid crystal panel 12 via a plurality of gate lines GLs in response to the video signal.
The related art LCD panel is affected by a driving circuit but is mainly affected by a characteristic of liquid crystal.
For example, when a ferroelectric liquid crystal (FLC) is used in the above-described LCD panel, a high resolution image is realized compared to existing generic liquid crystal. Due to a fast response speed, moving pictures may be realized, digital gray scale may be represented, and full color display and full digital driving may be performed in LCD's using FLC. In addition, pixel interference is reduced, and existing zigzag defects and chevron structure do not occur in a continuous director rotation (CDR) FLC mode.
As liquid crystal used in the LCD panel has been replaced with the FLC, there are more advantages compared to the use of existing liquid crystal. However, it is still difficult to obtain alignment stability and uniformity.
In particular, in case of amorphous silicon (a-Si) TFT-LCD, the driving circuit is attached after a liquid crystal process. In contrast, in case of a liquid crystal on silicon (LCoS) (or polysilicon TFT-LCD), the driving circuit is formed during a back panel process. Thus, in case of an LCoS panel, a liquid crystal alignment process using a well-known electric field alignment technology can be performed after an external controller is connected to the LCoS panel. As such, when stability and uniformity of the liquid crystal are lowered, a compensation procedure therefor is complicated.